Substrate processing method, substrate processing apparatus and recording medium

ABSTRACT

An ashing process in which an etching mask is removed through ashing by supplying hydrogen radicals toward a wafer W being heated to a predetermined temperature and a restoration process in which the film quality of a low dielectric constant insulating film having been damaged during an etching process is restored while, at the same time, rendering the low dielectric constant insulating film exposed at a recessed portion into a hydrophobic state by supplying a gas containing a β-diketone compound with an ignition point equal to or higher than 300° C. toward the wafer W having undergone the ashing process, are executed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This document claims priority to Japanese Patent Application Number2008-004951, filed on Jan. 11, 2008 and U.S. Provisional Application No.61/034,514, filed on Mar. 7, 2008, the entire content of which arehereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a substrate processing method, asubstrate processing apparatus and a recording medium, which may beadopted when continuously executing specific processes on a substratesuch as a semiconductor wafer or an FPD glass substrate.

BACKGROUND OF THE INVENTION

As an increasingly higher extent of integration is achieved insemiconductor integrated circuits in recent years, semiconductor devicesneed to adopt a multilayer wiring structure allowing wirings to bestacked over many layers. A semiconductor device adopting a multilayerwiring structure needs to include trench wiring that connects variouselements laid out along the horizontal direction and via-hole wiringthat connects various elements layered along the vertical direction. Alow-resistance metal with an outstanding anti-electromigration property,such as copper, is often used as the wiring material and a highly porouslow-k material that assures a low dielectric constant, is often used asthe interlayer insulating material so as to achieve higher speed in theintegrated circuit.

A wiring structure constituted with a low-dielectric constant insulatingfilm (hereafter may be referred to as a “low-k film”) and a copperwiring such as that described above, may be formed as described belowthrough, for instance, the damascene method. First, an insulating filmis formed on a semiconductor wafer (hereafter may be referred to as a“wafer”) which is the processing target substrate and a wiring layer isformed by burying a copper wiring in the insulating film. Next, anetching stopper film, an interlayer insulating film constituted of alow-k material, a capping film and an anti-reflection coating are formedin this order over the wiring layer. Then, a photoresist film with aspecific pattern corresponding to the wiring pattern is formed over theanti-reflection coating by using a photolithography technology. Thephotoresist film is used as a mask while etching through theanti-reflection coating, the capping film, the low-k film and theetching stopper film. As a result, a groove (trench) or a hole (via) tobe used as a wiring recess is formed at the low-k film, with the surfaceof the copper wiring exposed at the bottom of the wiring groove or thewiring hole.

Next, the wafer undergoes an ashing process to remove the photoresistfilm and the anti-reflection coating. Subsequently, a wiring metal,e.g., copper, is embedded in the wiring groove or the wiring hole formedat the low-k film, and finally, any excess metal is removed throughchemical-mechanical polishing (CMP). Part of the multilayer wiringstructure is completed by thus connecting the horizontal copper wiring(wiring layer) with the vertical copper wiring.

The low-k film, which has become an indispensable element in amultilayer wiring structure as described above, tends to be readilydamaged during the etching process or the ashing process. An area of thelow-k film subjected to such damage readily absorbs water and, as aresult, the dielectric constant over the area increases, resulting in anincrease in the parasitic capacity between the wirings, which, in turn,may lead to a signal delay and compromise the electrical characteristicssuch as the insulation resistance. For this reason, a restorationprocess for restoring the film quality by repairing the damaged area ofthe low-k film or by rendering the low-k film hydrophobic is executed onthe wafer having undergone the ashing process in the related art (see,for instance, patent reference literatures 1 and 2 listed below.

Today, a substrate processing apparatus equipped with a processingchamber where wafers undergo a specific type of processing must assurehigher throughput, miniaturization, efficient space utilization and thelike by continuously executing a plurality of types of processing withina single processing chamber. This requirement is addressed in substrateprocessing apparatuses that execute the ashing process and therestoration process as described above and substrate processingapparatuses capable of executing the ashing process and the restorationprocess within a single processing chamber have been proposed. Forinstance, patent reference literature 1 discloses a technology wherebyafter a wafer undergoes the etching process in a processing chamber, thewafer is ashed with oxygen radicals with the wafer temperature sustainedat approximately 100° C.˜150° C. and then a restoration process isexecuted on the ashed wafer by using a gas (hereafter referred to as a“silylating gas”) containing a silylating agent such as TMSDMA(dimethylaminotrimethyl silane) or DMSDMA (dimethylsilyldimethylamine)without transferring the wafer into another processing chamber.

It is also known that when the ashing process is executed with oxygenradicals, the low-k film may become damaged to result in a verysignificant increase in its dielectric constant. Accordingly, the use ofhydrogen radicals instead of oxygen radicals in the ashing process hasbeen proposed in recent years (see patent reference literatures 3through 5 listed below). An ashing process is normally executed withhydrogen radicals by setting the wafer temperature to a higher level(e.g., 250° C.˜400° C.) compared to the wafer temperature set for anashing process executed with oxygen radicals. While the amount of damageto the low-k film is reduced through the use of hydrogen radicals,damage still occurs during the etching process. For this reason, it isdesirable to execute a restoration process after the ashing processexecuted with hydrogen radicals.

However, the silylating gas used in the restoration processing in therelated art tends to ignite at a relatively low temperature. Forinstance, the ignition point (explosion limit temperature) of TMSDMA isapproximately 220° C. This means that the silylating gas may ignite asthe silylating gas to be use in the restoration process is deliveredinto the processing chamber if the temperature of the wafer havingundergone the ashing process in the same processing chamber is high.

The ashing process with oxygen radicals is executed with the wafertemperature set to a lower level (e.g., 100° C.˜150° C.) than theignition point of the silylating gas (220° C. in the case of TMSDMA, forinstance). Thus, the silylating gas delivered into the same processingchamber following the ashing process so as to immediately execute therestoration process in the processing chamber, is not likely to ignite.

Hydrogen radical processing, which is executed on the wafer sustaining ahigher temperature (e.g., 250° C.˜400° C.) than the wafer temperatureset for the oxygen radical processing, is more problematic in that asilylating gas with a low ignition point (e.g., 220° C.) delivered intothe same processing chamber for the restoration process following thehydrogen radical processing is highly likely to ignite.

In short, the restoration process in the related art, executed by usinga silylating gas with a low ignition point, cannot be executed in thesame processing chamber where the ashing process has been executed withhydrogen radicals. Since this requires allocation of separate processingchambers for the ashing process and the restoration process in, forinstance, a cluster-type substrate processing apparatus equipped with aplurality of processing chambers, miniaturization of the substrateprocessing apparatus and effective utilization of space have beenhindered. There is an added concern that if a failure occurs in eitherthe ashing process chamber or the restoration process chamber,continuous wafer transfer will be disabled.

-   (Patent reference literature 1) Japanese Laid Open Patent    Publication No. 2006-049798-   (Patent reference literature 2) Japanese Laid Open Patent    Publication No. 2006-111740-   (Patent reference literature 3) Japanese Laid Open Patent    Publication No. 2006-073722-   (Patent reference literature 4) Japanese Laid Open Patent    Publication No. 2007-128981-   (Patent reference literature 5) Japanese Laid Open Patent    Publication No. 2007-502543

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention, having been completedby addressing the issues discussed above, is to provide a substrateprocessing method and the like, which allow the restoration process tobe executed immediately within the same processing chamber following anashing process executed with hydrogen radicals.

The inventor of the present invention et al. found it of significantinterest that the ignition points of many gases containing a β-diketonecompound often used when forming a metal film in the related art arehigher, at 300° C. or more, than the ignition temperatures of thesilylating gases used in the related art. Tests conducted by theinventor of the present invention et al. revealed that a gas containinga β-diketone compound can be used in a restoration process executed torestore an area damaged during the etching process or the like.Furthermore, since such a gas, unlike the silylating gas used in therelated art, normally does not contain ammonia radicals, ammonia salt,which would settle onto the processing target substrate as particles, isnot readily formed on the processing target substrate. In addition, thedamaged area is dehydrated more effectively with the gas containing aβ-diketone compound than with the silylating gas in the related art.Based upon these findings indicating advantages of the use of a gascontaining a β-diketone compound in the restoration processing, theinventor of the present invention conceived the present invention, whichallows the ashing process executed with hydrogen radicals and therestoration process, requiring separate processing chambers in therelated art, to be executed in a single processing chamber through theuse of a gas containing a β-diketone compound with an ignition point of300° C. or higher in the restoration process.

The object described above is achieved in an aspect of the presentinvention by providing a substrate processing method adopted whenexecuting a specific type of processing on a processing target substratethat includes a low dielectric constant insulating film, an etching maskformed on the low dielectric constant insulating film and a recessedportion formed by etching with the etching mask the low dielectricconstant insulating film, comprising an ashing process step in which theetching mask is removed through ashing with hydrogen radicals deliveredto the processing target substrate, heated to sustain a predeterminedtemperature and a restoration process step in which the low dielectricconstant insulating film exposed at the recessed portion is renderedhydrophobic and the film quality of the low dielectric constantinsulating film having been damaged in the etching process is restoredwith a gas containing a β-diketone compound with an ignition pointthereof equal to or higher than 300° C., delivered to the processingtarget substrate having undergone the ashing process.

The object described above is also achieved in another aspect of thepresent invention by providing a computer-readable recording mediumhaving recorded therein a program that enables a computer to executevarious steps of a substrate processing method adopted when executing aspecific type of processing on a processing target substrate thatincludes a low dielectric constant insulating film, an etching maskformed on the low dielectric constant insulating film and a recessedportion formed by etching with the etching mask the low dielectricconstant insulating film. The program enables the computer to execute anashing process step in which the etching mask is removed through ashingwith hydrogen radicals delivered to the processing target substrate,heated to sustain a predetermined temperature and a restoration processstep in which the low dielectric constant insulating film exposed at therecessed portion is rendered hydrophobic and the film quality of the lowdielectric constant insulating film having been damaged in the etchingprocess is restored with a gas containing a β-diketone compound with anignition point thereof equal to or higher than 300° C., delivered to theprocessing target substrate having undergone the ashing process.

According to the present invention described above, a gas containing aβ-diketone compound with an ignition point of 300° C. or higher, i.e.,higher than the ignition points of the gases used in the related art, isused in the restoration process. Thus, following the ashing processexecuted with hydrogen radicals on the processing target substratesustained at a relatively high temperature, the restoration process canbe successively executed within the same processing chamber. As long asthe temperature of the processing target substrate following the ashingprocess is sufficiently lower than the ignition point, the restorationprocess can be executed by using the β-diketone compound-containing gasimmediately afterwards. Thus, a great improvement in throughput over therelated art, in which the different types of processing must be executedin separate processing chambers, is achieved. It is to be noted thatdepending upon the processing conditions, the temperature of theprocessing target substrate immediately after the ashing process may behigher than the ignition point. However, even under such circumstances,the restoration process can be executed with the β-diketonecompound-containing gas after allowing the processing target substrateto cool down to a temperature lower than the ignition point. In thiscase, too, only a short wait time is required following the ashingprocess before the restoration process can be executed, since theignition point of the gas used in the restoration process according tothe present invention is 300° C. or higher, which is higher than theignition points of the gases used in the related art. As a result, thethroughput is not lowered significantly.

In addition, the film quality of the damaged area of the low dielectricconstant insulating film, having become damaged during the etchingprocess, is restored to a desirable condition and the damaged area canbe dehydrated more readily and effectively compared to the related art.

It is desirable that the ashing process and the restoration process beexecuted in a single processing chamber, so as to eliminate the need toallocate separate processing chambers for the ashing process and therestoration process. Through these measures, miniaturization and moreefficient utilization of space are achieved for the substrate processingapparatus.

According to the present invention, the temperature of the processingtarget substrate may be measured following the ashing process step, therestoration process may be executed immediately afterwards as long asthe measured temperature of the processing target substrate is lowerthan a predetermined temperature set within a range lower than theignition point of the gas used in the restoration process, but therestoration process may be executed only after the processing targetsubstrate is cooled to a temperature lower than the predeterminedtemperature if the measured temperature of the processing targetsubstrate is equal to or higher than the predetermined temperature.Through these measures, it is ensured that even when the temperature ofthe processing target substrate following the ashing process is higherthan the ignition point, the processing target substrate is allowed tocool down to a temperature sufficiently lower than the ignition point.Since the length of wait time to elapse before the restoration processis executed is minimized through the temperature monitoring, betterthroughput is achieved.

The β-diketone compound may be, for instance, dipivaloylmethane (DPM) oracetylacetone. The ignition point of dipivaloylmethane is approximately300° C., whereas the ignition point of acetylacetone is approximately350° C. Namely, either gas with a much higher ignition point compared tothe silylating gases used in the related art, can be used in therestoration process according to the present invention to assumesignificant advantages. In addition, unlike the silylating gasescontaining ammonia groups used in the related art, neither gas containsan ammonia group and thus neither gas readily forms ammonium salt, whichwould settle as particles on the processing target substrate. Moreover,either gas is highly effective in restoring the damaged area and inducesa desirable dehydrating reaction to dehydrate the damaged area moreeffectively than the silylating gases used in the related art.

The object described above is further achieved in yet another aspect ofthe present invention by providing a substrate processing apparatusequipped with a processing chamber where a specific type of processingis executed on a processing target substrate that includes a lowdielectric constant insulating film, an etching mask formed on the lowdielectric constant insulating film and a recessed portion formed byetching with the etching mask the low dielectric constant insulatingfilm. The processing chamber comprises a plasma generation chamber wherehydrogen plasma is generated, a main processing chamber communicatingwith the plasma generation chamber, a stage disposed within the mainprocessing chamber, upon which the processing target substrate isplaced, a temperature adjustment unit that adjusts the temperature ofthe processing target substrate placed on the stage to a predeterminedtemperature, a hydrogen-containing gas supply unit that supplies ahydrogen-containing gas into the plasma generation chamber, an inductionfield forming unit that forms within the plasma generation chamber aninduction field used to generate the hydrogen plasma, a β-diketonecompound-containing gas supply unit that supplies a β-diketonecompound-containing gas that contains a β-diketone compound with anignition point equal to or higher than 300° C., toward the surface ofthe processing target substrate placed on the stage, and a exhaustdevice that evacuates the processing chamber.

According to the present invention described above, the ashing processexecuted with hydrogen radicals on the processing target substratehaving undergone the etching process, and the restoration process can beexecuted immediately within the same processing chamber. Namely, theprocessing target substrate placed on the stage within the mainprocessing chamber is heated to a specific temperature via thetemperature adjustment unit. Then, as the hydrogen-containing gas issupplied from the hydrogen-containing gas supply unit into the plasmageneration chamber, the processing chamber is evacuated and with thepressure inside the processing chamber thus sustained at a predeterminedlevel, plasma is generated by forming an induction field via theinduction field forming unit. The processing target substrate on thestage is ashed with hydrogen radicals generated from the plasma.Subsequently, the β-diketone compound-containing gas is supplied fromthe β-diketone compound-containing gas supply unit, and with theβ-diketone compound-containing gas thus supplied, the restorationprocess is executed to restore the film quality of the low dielectricconstant insulating film having been damaged during the etching processor the like while, at the same time, rendering hydrophobic the lowdielectric constant insulating film exposed at the recessed portion.

The temperature adjustment unit may include a cooling unit that coolsthe processing target substrate placed on the stage and a heating unitthat heats the processing target substrate placed on the stage. Withsuch a temperature adjustment unit, the processing target substrate canbe heated quickly for the ashing process and the processing targetsubstrate can also be cooled quickly prior to the restoration process ifthe processing target substrate temperature is too high. As a result, animprovement in throughput is achieved when the ashing process and therestoration process are executed continuously.

The present invention provides a substrate processing method and thelike, which, through the use of a gas with an ignition point higher thanthose of the gases used in the related art for the restoration process,allow the restoration process to be executed immediately within the sameprocessing chamber after an ashing process executed with hydrogenradicals at a relatively high temperature.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a lateral sectional view presenting an example of a structurethat may be adopted in the substrate processing apparatus achieved in anembodiment of the present invention;

FIG. 2 is a block diagram presenting an example of a structure that maybe adopted in the control unit in FIG. 1;

FIG. 3 is a longitudinal sectional view presenting an example of astructure that may be adopted in the post processing chambers in thesubstrate processing apparatus in the embodiment;

FIG. 4 is a sectional view presenting a specific example of a filmstructure that may be assumed in a wafer in the pre-processing state,before undergoing processing in the substrate processing apparatus inthe embodiment;

FIG. 5 presents a flowchart of the wafer processing executed in thesubstrate processing apparatus in the embodiment;

FIG. 6 is a sectional view presenting a specific example of a filmstructure that may be assumed at the wafer following the etchingprocess;

FIG. 7 is a sectional view presenting a specific example of a filmstructure that may be assumed at the wafer following the ashing process;

FIG. 8 is a sectional view presenting a specific example of a filmstructure that may be assumed at the wafer following the restorationprocess;

FIG. 9A illustrates part of the process through which particles areformed on the wafer having undergone the etching process;

FIG. 9B illustrates part of the process through which particles areformed on the wafer having undergone the etching process;

FIG. 9C illustrates part of the process through which particles areformed on the wafer having undergone the etching process;

FIG. 9D illustrates part of the process through which particles areformed on the wafer having undergone the etching process;

FIG. 10 is a graph presenting the results obtained by measuring thedielectric constant of the low-k film formed on test wafers havingundergone the etching process, the ashing process and the restorationprocess; and

FIG. 11 is a graph presenting the results obtained by measuring thecontact angle of a liquid dropped onto the low-k film formed on testwafers having undergone the etching process, the ashing process and therestoration process.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The following is a detailed description of a preferred embodiment of thepresent invention, given in reference to the attached drawings. It is tobe noted that in the description and the drawings, the same referencenumerals are assigned to components assuming substantially identicalfunctions and structural features, so as to preclude the necessity for arepeated explanation thereof.

(Structural Example for the Substrate Processing Apparatus)

The substrate processing apparatus achieved in the embodiment of thepresent invention is explained first in reference to the drawings. FIG.1 schematically illustrates the structure adopted in the substrateprocessing apparatus achieved in the embodiment of the presentinvention. The substrate processing apparatus 100 comprises a processingunit 200 equipped with a plurality of processing chambers where varioustypes of processing such as an etching process, an ashing process andprocessing for restoring a film having been damaged during the etchingprocess and the ashing process to a desirable condition (hereafter alsoreferred to as a “restoration process”) are executed on substrates suchas semiconductor wafers W in a low pressure environment, an atmosphericpressure-side transfer unit 300 via which a wafer W is carried into/outof the processing unit 200 and a control unit 120 that executes overallcontrol for the operations executed in the substrate processingapparatus 100.

The transfer unit 300 includes an atmospheric pressure-side transferchamber 310 via which the wafer W is transferred between a substratestorage container such as a cassette container 102 (102A˜102C) and theprocessing unit 200. The transfer chamber 310 is formed in a box shapewith a substantially polygonal section. A plurality of cassette stages302 (302A˜302C) are set next to one another along one of the sidesurfaces of the transfer chamber 310 ranging along the longer side ofits substantially polygonal section. The cassette containers 102A˜102Ccan be placed respectively upon the cassette stages 302A˜302C.

At each of the cassette containers 102 (102A˜102C), up to, for instance,25 wafers W, with their ends held by a holding portion, are stacked overmultiple levels with a uniform pitch for storage. The cassettecontainers have a sealed structure that allows the inner spaces to befilled with, for instance, nitrogen (N2) gas. At the side surface of thetransfer chamber 310, along which the plurality of cassette stages 302(302A˜302C) are disposed side-by-side, transfer ports 314 (314A˜314C)are formed and wafers W can thus be transferred between the individualcassette containers 102 (102A˜102C) and the transfer chamber 310 via thetransfer ports 314 (314A˜314C). It is to be noted that the numbers ofthe cassette stages 302 and the cassette containers 102 in the substrateprocessing apparatus are not limited to the examples presented in FIG.1.

At an end of the transfer chamber 310, i.e., at a side surface of thetransfer chamber ranging along the shorter side of its substantiallypolygonal section, an orienter (pre-alignment stage) 304 to function asa positioning device, which includes a rotary stage 306 and an opticalsensor 308 for optically detecting the edge of a wafer W, both providedas built-in units, is located. The orienter 304 positions the wafer W bydetecting, for instance, an orientation flat or a notch at the wafer W.

Inside the transfer chamber 310, a transfer unit-side transfer mechanism320 which transfers the wafer W along the lengthwise direction(indicated by the arrow in FIG. 1) is disposed. A base 322 to which thetransfer unit-side transfer mechanism 320 is fixed is slidably supportedon a guide rail 324 laid along the lengthwise direction inside thetransfer chamber 310. A mover and a stator of a linear motor arerespectively disposed at the base 322 and the guide rail 324. At an endof the guide rail 324, a linear motor drive mechanism (not shown) viawhich the linear motor is driven is disposed. As the linear motor drivemechanism is controlled based upon a control signal sent by the controlunit 120, the transfer unit-side transfer mechanism 320 moves along thelengthwise direction on the guide rail 324 together with the base 322.

The transfer unit-side transfer mechanism 320 adopts a double armstructure, which includes two arm units. In addition, the arm units arearticulated, which allows them to extend, retract, move up/down andswing freely to the sides. End effectors 326A and 326B used to holdwafers W are mounted at the front ends of the arms and thus, thetransfer unit-side transfer mechanism 320 is able to handle two wafers Wat once. Via this transfer unit-side transfer mechanism 320, wafers Wcan be carried into/out of, for instance, the cassette containers 102,the orienter 304, and first and second loadlock chambers 230M and 230Nto be detailed later so as to replace a wafer W present in the chamberwith a new wafer W. A sensor (not shown) capable of detecting thepresence of a wafer W held thereat is mounted at each of the endeffectors 326A and 326B of the transfer unit-side transfer mechanism320. It is to be noted that the number of arm units in the transferunit-side transfer mechanism 320 is not limited to that described aboveand the transfer unit-side transfer mechanism 320 may adopt, forinstance, a single arm structure that includes a single arm unit,instead.

Next, a structural example that may be adopted in the processing unit200 is described. The processing unit 200 in the cluster tool-typeprocessing apparatus 100 in the embodiment includes a common transferchamber 210 formed to have a polygonal (e.g., a hexagonal) section, aplurality of processing chambers 220 (first through sixth processingchambers 220A˜220F) connected around the common transfer chamber whilesustaining air tightness and the first and second loadlock chambers 230Mand 230N as shown in FIG. 1.

In the processing chambers 220A˜220F, a specific single type ofprocessing or specific different types of processing, e.g., an ashingprocess and a restoration process to be detailed later as well asetching, are executed on wafers W based upon process recipes and thelike stored in advance in a storage medium or the like in the controlunit 120. Stages 222 (222A˜222F) upon which wafers W are placed arerespectively disposed inside the individual processing chambers 220(220A˜220F). The structures adopted in the individual processingchambers 220 are to be detailed later. It is to be noted that the numberof processing chambers 220 is not limited to that shown in FIG. 1.

The common transfer chamber 210 adopts a structure that allows itsinternal space to be controlled to maintain a specific degree of vacuum.Via the common transfer chamber, wafers W are carried to be transferredamong the individual processing chambers 220A˜220F and also from theindividual chambers 220A˜220F to the first and second loadlock chambers230M and 230N. The common transfer chamber 210 is formed in a polygonalshape (e.g., a hexagonal shape), with the processing chambers 220(220A˜220F) connected around the common transfer chamber via gate valves240 (240A˜240F) respectively, with the front ends of the first andsecond loadlock chambers 230M and 230N also connected around the commontransfer chamber via gate valves (low pressure-side gate valves) 240Mand 240N respectively. The base ends of the first and second loadlockchambers 230M and 230N are connected to the other side surface of thetransfer chamber 310 ranging along the longer side of the substantiallypolygonal section, respectively via gate valves (atmosphericpressure-side gate valves) 242M and 242N.

The first and second loadlock chambers 230M and 230N have a function oftemporarily holding wafers W and passing them on to the next processupon completing pressure adjustment. Inside the first and secondloadlock chambers 230M and 230N, transfer stages 232M and 232N uponwhich wafers W can be placed are respectively disposed.

Inside the common transfer chamber 210, a processing unit-side transfermechanism 250 constituted with articulated arms capable of extending,retracting, moving up/down and swinging to the sides are disposed. Theprocessing unit-side transfer mechanism 250 includes two end effectors252A and 252B, which enable it to handle two wafers W at once. Inaddition, the processing unit-side transfer mechanism 250 is rotatablysupported at a base 254. The base 254 slides freely on a guide rail 256laid out to range from the base end side toward the front end sideinside the common transfer chamber 210 via, for instance, a slide-drivemotor (not shown). It is to be noted that a flexible arm 258, throughwhich the wiring for, for instance, an arm swinging motor and the likepasses is connected to the base 254. The processing unit-side transfermechanism 250 structured as described above is able to access the firstand second loadlock chambers 230M and 230N and the individual processingchambers 220A˜220F by sliding along the guide rail 256.

For instance, the processing unit-side transfer mechanism 250 should bepositioned toward the base end side in the common transfer chamber 210along the guide rail 256 in order to access the first or second loadlockchamber 230M or 230N or either of the processing chambers 220A and 220Ffacing opposite each other. In order to access any of the fourprocessing chambers 220B˜220E, the processing unit-side transfermechanism 250 should be positioned toward the front end side of thecommon transfer chamber 210 along the guide rail 256. Thus, all theprocessing chambers 220A˜220F and both the first loadlock chamber 230Mand the second loadlock chamber 230N, each connected to the commontransfer chamber 210, can be accessed via a single processing unit-sidetransfer mechanism 250.

It is to be noted that the processing unit-side transfer mechanism 250may adopt a structure other than that described above and may include,for instance, two transfer mechanisms. Namely, a first transfermechanism constituted with an articulated arm capable of extending,retracting, moving up/down and swinging to the sides may be disposedtoward the base end side of the common transfer mechanism 210 and asecond transfer mechanism constituted with an articulated arm capable ofextending, retracting, moving up/down and swinging to the sides may bedisposed toward the front end side of the common transfer chamber 210.In addition, the number of end effectors in the processing unit-sidetransfer mechanism 250 does not need to be two and the processingunit-side transfer mechanism may instead include a single end effector.

(Structural Example for the Control Unit)

Next, a specific structural example that may be adopted in the controlunit 120 is described in reference to a drawing. FIG. 2 is a blockdiagram showing the structure adopted in the control unit 120. Asexplained earlier, the control unit 120 controls the overall operationsexecuted in the substrate processing apparatus 100, such as waferprocessing control under which wafers W are processed in the individualprocessing chambers 220, displacement control for the transfer unit-sidetransfer mechanism 320 and the processing unit-side transfer mechanism250, open/close control for the various gate valves 240 and 242 androtation control for the rotary stage 306 at the orienter 304.

The control unit 120 that executes such control includes a CPU (centralprocessing unit) 120 constituting the main body of the control unit, aROM (read-only memory) 124 in which data and the like used by the CPU122 to control the individual units are stored, a RAM (random-accessmemory) 126 having a memory area used for various types of dataprocessing executed by the CPU 122 and the like, a display unit 128constituted with a liquid crystal display or the like, at whichoperation screens, selection screens and the like are brought up ondisplay, an operation unit (input/output unit) 130 via which theoperator is able to input/output various types of data, an alerting unit132 constituted with an alarm device such as a buzzer, variouscontrollers 134 functioning as module controllers that individuallycontrol specific module units such as the processing chambers 220A˜220F,the common transfer chamber 210, the atmospheric pressure-side transferchamber 310 and the orienter 304 in the substrate processing apparatus100, and a storage unit 140 for storing program data constitutingvarious programs used in the substrate processing apparatus 100 andvarious types of setting information used when program processing isexecuted based upon the program data.

In the storage unit 140, a transfer program 142, based upon which theoperations of the transfer unit-side transfer mechanism 320 and theprocessing unit-side transfer mechanism 250 are controlled, and aprocessing program 144 executed when processing wafers W in theprocessing chambers 220 are stored. In addition, process recipe data 146indicating processing conditions, e.g., the chamber internal pressures,the gas flow rates, the high frequency power levels and the like, underwhich the processing is to be executed in the individual processingchambers 220 are stored in the storage unit 140. The data stored in thestorage unit 140, which may be constituted with a recording medium suchas a flash memory, a hard disk or a CD-ROM, are read out by the CPU 122as necessary.

The CPU 122, the ROM 124, the RAM 126, the display unit 128, theoperation unit 130, the alerting unit 132, the various controllers 134and the storage unit 140 constituting the control unit 120 areelectrically connected with one another via a bus line 150 which may bea control bus, a system bus or a data bus.

(Structural Examples for the Processing Chambers)

Next, structural examples that may be adopted in the processing chambersof the substrate processing apparatus 100 shown in FIG. 1 are described.The substrate processing apparatus 100 may adopt a structure that allowsan etching process through which a low-k film formed on the wafer W isselectively etched in a specific pattern and post processes, i.e., anashing process for removing the etching mask having been used in theetching process and a restoration process for restoring the film qualityof the low-k film, to be executed continuously. In addition, theprocessing chambers 220A, 220B, 220E and 220F, for instance, may beassigned to function as etching process chambers and the processingchambers 220C and 220D may be assigned to function as processingchambers (hereafter may also be referred to as “post processingchambers”) where the post processes, i.e., the ashing process and therestoration process are executed in succession on a wafer W havingundergone the etching process. It is to be noted that by adjusting thecombination of processing designations to the individual processingchambers 220A˜220F, the details of the actual processing to be executedin the substrate processing apparatus 100 can be altered.

The etching process chambers among the plurality of processing chambersin the substrate processing apparatus 100 assume a structure thatenables selective etching of the low-k film formed on the wafer W in aspecific pattern by raising to plasma a processing gas delivered intothe chamber internal space sustaining a low pressure (e.g., 100 mTorr)and delivering ions and radicals generated as the processing gas israised to plasma to the wafer W. The processing gas used in the etchingprocess may be, for instance, CF₄ gas, CHF₃ gas, C₄F₈ gas, O₂ gas, Hegas, Ar gas, N₂ gas or a mixed gas containing such gases in combination.

(Structural Examples for the Post Processing Chambers)

In reference to a drawing, an example of a structure that may be adoptedin the post processing chambers is described. As explained earlier, theprocessing chambers 220C and 220D in the substrate processing apparatus100 achieved in the embodiment assume a structure that enables them tofunction as post processing chambers, where the ashing process forremoving the etching mask having been used in the etching process andthe restoration process for restoring the film quality of the low-k filmhaving been damaged during the etching process, can both be executed insuccession. FIG. 3 schematically illustrates the structure adopted in apost processing chamber 400 in the embodiment.

As shown in FIG. 3, the post processing chamber 400 includes asubstantially cylindrical main processing chamber 402 and asubstantially cylindrical bell jar 404 to function as a plasmageneration chamber, which is disposed above the main processing chamberin communication with the main processing chamber 402.

At the side wall of the main processing chamber 402, a transfer port406, via which the wafer W is transferred out of/into the mainprocessing chamber 402, is present and the gate valve 240 describedearlier is mounted at the transfer port 406. As the gate valve 240 isopened, the wafer W can be carried between the post processing chamber400 and a chamber adjacent to the post processing chamber, i.e., thecommon transfer chamber 210 in this example.

A stage 408 constituted of ceramic, such as aluminum nitride (AlN), viawhich the wafer W is supported in a level state, is disposed within themain processing chamber 402. The stage 408 includes a cylindrical baseportion 410 formed at the bottom surface of the main processing chamber402 and a faceplate 412 for supporting the wafer W, mounted levelly atthe upper surface of the base portion 410. The faceplate 412 is a diskslightly larger than the wafer W. The faceplate 412 is constituted of amaterial with superior thermal conductivity, such as silicon carbide(SiC) or aluminum nitride.

At the upper surface of the stage 408 (at the upper surface of thefaceplate 412), a plurality of contact pins 414 to contact the lowersurface of the wafer W, ranging upright, are disposed. The contact pins414 are constituted of a material identical to that constituting thefaceplate 412, such as ceramic or resin. The wafer W, with its lowersurface held at the upper ends of the plurality of contact pins 414, isthus supported in a level state. It is to be noted that a liftermechanism (not shown) used to place the wafer W transferred into themain processing chamber 402 onto the upper surface of the stage 408 andto lift the wafer off the upper surface of the stage 408, is disposed tosurround the wafer W.

On the rear surface (lower surface) side of the faceplate 412, atemperature adjustment unit that adjusts the temperature of the wafer Wplaced on the upper surface of the faceplate 412 to a predeterminedtemperature is installed. The temperature adjustment unit is constitutedwith a cooling unit that lowers the temperature of the wafer W placed onthe upper surface of the faceplate 412 and a heating unit that raisesthe temperature of the wafer W placed on the upper surface of thefaceplate 412.

More specifically, a heater 416 constituting the heating unit is mountedin close contact with the rear surface (lower surface) of the faceplate412. The heater 416 is constituted of a material having superior thermalconductivity, which generates heat as power is supplied thereto, such asSiC. A heater power source 418 is electrically connected to the heater416 and the wafer W placed on the upper surface of the faceplate 412 canbe heated to a specific temperature and is allowed to sustain thetemperature at the specific level with the power supplied from theheater power source 418 to the heater 416, which is adjusted to theoptimal level. The heater 416 assumes the shape of a disk having adiameter substantially equal to that of the wafer W. Thus, the heat fromthe heater 416 can be distributed evenly to the entire wafer W via thefaceplate 412 so as to uniformly heat the wafer W as a whole.

A cooling block 420 constituting the cooling unit is disposed under theheater 416. The cooling block 420 is allowed to move up/down via anelevator device 424 such as a cylinder supported at a bracket 422 fixedto the lower surface of the main processing chamber 402. Morespecifically, the cooling block 420 alternately assumes a state in whichit is in contact with the lower surface of the heater 416 (a state inwhich the cooling block 420 is in thermal communication with thefaceplate 412) and a state in which it is set apart from the lowersurface of the heater 416 (a state in which the cooling block 420 isthermally isolated from the faceplate 412). It is to be noted that thecooling block 420 assumes the shape of a circular column with a diametersubstantially equal to the diameter of the wafer W and the entire uppersurface of the cooling block in the elevated state contacts the rearsurface of the heater 416.

Inside the cooling block 420, a coolant passage 426, through which acoolant such as a fluorine group inert chemical (e.g., GALDEN) travelsis formed. As the coolant, having entered a coolant supply piping 428,circulates through the coolant passage 426 and then exits the coolantpassage via a coolant discharge piping 430, the cooling block 420 iscooled to, for instance, approximately 25° C. It is to be noted that thecoolant supply piping 428 and the coolant discharge piping 430 are eachconstituted with a bellows, a flexible tube or the like, so as to ensurethat the delivery/discharge of the coolant is not hindered by thecoolant block 420 as it moves up/down via the elevator device 424mentioned earlier.

The wafer W placed on the upper surface of the faceplate 412 can becooled quickly with the cooling block 420 raised via the elevator device424 and set in contact with the lower surface of the heater 416. Sincethe cooling block 420 assumes the shape of a disk with a diametersubstantially equal to that of the wafer W, the heat originating fromthe entire wafer W can be transferred to the cooling block 420 via thefaceplate 412 and the heater 416, and thus, the whole wafer W can becooled evenly.

The overall thermal capacity, representing that sum of the thermalcapacities of the faceplate 412 and the heater 416, is set lower thanthe thermal capacity of the cooling block 420. In more specific terms,the faceplate 412 and the heater 416 both assume shapes that will ensurethat they have relatively small thermal capacities, e.g., a shape with asmall thickness, and they are both constituted of a material with goodthermal conductivity, such as SiC. The cooling block 420, on the otherhand, assumes the shape of a circular column with a thickness greaterthan the sum of the thicknesses of the faceplate 412 and the heater 416.

When the cooling block 420 is raised and in contact with the lowersurface of the heater 416, heat is transferred from the heater 416, thefaceplate 412 and the wafer W placed on the upper surface of thefaceplate 412 to the cooling block 420. Since the thermal capacity ofthe cooling block 420 is considerably greater than the thermalcapacities of the heater 416, the faceplate 412 and the wafer W, thewafer W placed on the upper surface of the faceplate 412 can be quicklycooled.

When the cooling block 420 is in the lowered state, away from the lowersurface of the heater 416, the faceplate 412 can be heated with bysupplying power to the heater 412. Since the thermal capacity of thefaceplate 412 is relatively small, the faceplate 412 can be promptlyheated to a specific temperature and as the faceplate 412 is thusheated, the wafer W placed on the upper surface of the faceplate 412 isalso rapidly heated.

A temperature sensor head such as a thermocouple 432 is installed at thefaceplate 412. An electrical signal (voltage) generated at thethermocouple 432 indirectly indicates the temperature of the wafer Wplaced on the upper surface of the faceplate 412. Based upon theelectrical signal received from the thermocouple 432, the control unit120 is able to control the level of the power output from the heaterpower source 418 and move up/down the cooling block by controlling theoperation of the elevator device 424, so as to adjust the temperature ofthe wafer W to the specific level within a range of, for instance, 180°C.˜400° C.

A discharge pipe 434 is connected to the bottom wall of the mainprocessing chamber 402 and a exhaust device 436 equipped with a vacuumpump such as a turbo molecular pump is connected to the discharge pipe434. By engaging the exhaust device 436 in operation, the pressureinside the main processing chamber 402 and the bell jar 404 can bereduced until a predetermined degree of vacuum is achieved.

The bell jar 404, constituted of an electrically insulating materialsuch as quartz or ceramic, includes an induction field forming unit thatforms an induction field to be used to generate hydrogen plasma insidethe bell jar. The induction field forming unit is constituted with acoil 440 wound around the bell jar 404 and a high-frequency power source442 connected to the coil 440 and capable of supplying high-frequencypower with the frequency set within a range of, for instance, 300 kHz˜60MHz. By adjusting the level and frequency of the high-frequency powersupplied from the high-frequency power source 442 to the coil 440, aninduction field with a specific, desired level of intensity can beformed inside the bell jar 404.

In the post processing chamber 400 structured as described above, plasmacan be generated through the inductively coupled plasma (ICP) method.Since the plasma is generated in the space above and away from the waferW, the post processing chamber may also be referred to as a “remoteplasma-type (or a downflow plasma-type)” chamber. It is to be noted thatwhile hydrogen plasma is formed through the inductively coupled plasmamethod in the post processing chamber 400 in the embodiment, the presentinvention is not limited to this example and it may be adopted inconjunction with, for instance, hydrogen plasma generated through themicrowave excitation method. It may also be adopted in conjunction withhydrogen radicals (atomic hydrogen) H* generated by placing ahydrogen-containing gas in contact with a high temperature catalyser(e.g., a high temperature catalyst wire).

A processing gas supply piping 444 is connected at the ceiling wall ofthe bell jar 404. A hydrogen-containing gas supply unit and a β-diketonecompound-containing gas supply unit are connected to the processing gassupply piping 444. The hydrogen-containing gas supply unit comprises anashing processing gas supply source 450 from which a hydrogen-containinggas to be used as an ashing processing gas is output, an ashingprocessing gas supply piping 452 connecting the ashing processing gassupply source 450 with the processing gas supply piping 444 and a massflow controller 454 and a switching valve 456 disposed at the ashingprocessing gas supply piping 452. The ⊖-diketone compound-containing gassupply unit comprises a restoration processing gas supply source 460from which a gas containing a β-diketone compound with an ignition pointequal to or higher than 300° C., to be used as a restoration processinggas, is output, a restoration processing gas supply piping 462connecting the restoration processing gas supply source 460 with theprocessing gas supply piping 444 and a mass flow controller 464 and aswitching valve 466 disposed at the restoration processing gas supplypiping 462.

The operations of the mass flow controllers 454 and 464 and theswitching valves 456 and 466 are controlled by the control unit 120.Thus, the control unit 120 is able to select a specific processing gas(the ashing processing gas or the restoration processing gas) to bedelivered into the post processing chamber 400 and adjust the flow ratesof the various processing gases based upon the processing condition(process recipe) data 146 stored in the storage unit 140.

A gas with which hydrogen radicals (atomic hydrogen) H* can begenerated, e.g., hydrogen gas or a mixed gas containing hydrogen gas andan inert gas (such as helium gas, argon gas or neon gas), is used as theashing processing gas in the embodiment. A mixed gas used as the ashingprocessing gas should contain hydrogen gas mixed with its ratio adjustedto, for instance, 4%.

In addition, the restoration processing gas used in the embodimentshould contain a β-diketone compound with an ignition point equal to orhigher than 300° C. More specifically, a gas containingdipivaloylmethane (DPM) (hereafter referred to as “DPM gas”) or a gascontaining acetylacetone (hereafter referred to as “acetylacetone gas”)may be used. The structural formulae (A) for DPM and the structuralformulae (B) for acetylacetone are provided below.

The wafer W undergoes the ashing process in the post processing chamber400 structured as described above, with its temperature raised to thespecific level (e.g., 250° C.) while the hydrogen-containing gas used asthe ashing processing gas is supplied into the bell jar 404 and thehigh-frequency power is supplied from the high-frequency power source442 to the coil 440. With the induction field formed inside the bell jar404 as a result, plasma is generated from the hydrogen-containing gasinside the bell jar 404 and hydrogen radicals H* are thus generated. Thehydrogen radicals are then delivered to the wafer W placed on the stage408 and the wafer W is ashed with the hydrogen radicals. Through thisprocess, the etching mask on the wafer W is removed.

The wafer W undergoes the restoration process in the post processingchamber 400 with its temperature adjusted to the same level (e.g., 250°C.) as that set for the ashing process while the DPM gas or theacetylacetone gas to be used as the restoration processing gas isdelivered into the post processing chamber 400. With the DPM gas or theacetylacetone gas delivered to the wafer W placed on the stage 408, thelow-k film on the wafer W, having been damaged during the etchingprocess or the ashing process, can be restored to good condition.

As described above, the DPM gas or the acetylacetone gas with inignition point of 300° C. or higher, higher than the ignition points ofthe processing gases used in the related art, is delivered into the postprocessing chamber 400 to be used for the restoration process, inaddition to the gas used for the hydrogen radical ashing process. Thus,the restoration process can be executed in succession in the same postprocessing chamber 400 following the ashing process. The ashing processand the restoration process executed in the post processing chamber 400are to be described in detail later.

A silylating gas such as TMSDMA or DMSDMA is normally used as therestoration processing gas when restoring the low-k film damaged duringthe etching process or the ashing process in the related art. However,silylating gases tend to ignite at relatively low temperatures. Forinstance, the ignition point of a gas containing TMSDMA (hereafter maybe referred to as a “TMSDMA gas”) is approximately 220° C. This meansthat the silylating gas delivered into the processing chamber for therestoration process may ignite if the temperature of the wafer havingundergone the ashing process in the same processing chamber is high.

The ashing process with oxygen radicals is executed with the wafertemperature set to a lower level (e.g., 100° C.˜150° C.) than theignition point of the silylating gas (220° C.). Thus, the silylating gasdelivered into the same processing chamber following the ashing processso as to immediately execute the restoration processing in theprocessing chamber is not likely to ignite. Hydrogen radical processing,which is executed on the wafer sustaining a higher temperature (e.g.,250° C.˜400° C.) than the wafer temperature set for the oxygen radicalprocessing, is more problematic in that a silylating gas with a lowignition point (e.g., 220° C.) delivered into the same processingchamber for the restoration process following the hydrogen radicalprocessing is highly likely to ignite. In short, the restoration processin the related art, executed by using a silylating gas with a lowignition point, cannot be executed in the same processing chamber wherethe ashing process has been executed with hydrogen radicals.

The inventor of the present invention et al. found it of significantinterest that the ignition points of many gases containing a β-diketonecompound often used when forming a metal film in the related art, arehigher, at 300° C. or more, than the ignition temperatures of thesilylating gases used in the related art. The ignition point of DPM gasthat contains a β-diketone compound is 300° C., whereas the ignitionpoint of an acetylacetone gas also containing a β-diketone compound is350° C., both higher than the ignition point of a silylating gas (theignition point of, for instance, a TMSDMA gas is 220° C.).

Tests conducted by the inventor of the present invention et al. revealedthat a gas containing a β-diketone compound can be used in a restorationprocess executed to restore an area damaged during the etching processor the like. It was further learned that significantly greateradvantages are achieved by using a β-diketone compound-containing gas inthe restoration process, as detailed later, than those achieved throughthe restoration process executed by using a silylating gas.

In the embodiment conceived based upon these findings indicatingadvantages of the use of a gas containing a β-diketone compound in therestoration process, the ashing process executed with hydrogen radicalsand the restoration process, requiring separate processing chambers inthe related art, are executed in a single post processing chamber 400made possible through the use of a gas containing a β-diketone compoundwith an ignition point of 300° C. or higher (e.g., DPM gas oracetylacetone gas) in the restoration process.

According to the present invention described above, a gas containing aβ-diketone compound with an ignition point of 300° C. or higher, i.e.,higher than the ignition points of the gases used in the related art, isused in the restoration process. Thus, following the ashing processexecuted with hydrogen radicals on the processing target substratesustained at a relatively high temperature, the restoration process canbe executed continuously within the same post processing chamber 400. Aslong as the temperature of the wafer following the ashing process issufficiently lower than the ignition point, the restoration process canbe executed by using the β-diketone compound-containing gas immediatelyafterwards. Thus, an improvement in throughput over the related art, inwhich the different processes must be executed in separate processingchambers, is achieved.

In addition, depending upon the processing conditions, the temperatureof the wafer immediately after the ashing process may be higher than theignition point. However, even under such circumstances, the restorationprocess can be executed with the β-diketone compound-containing gasafter allowing the processing target substrate to cool down to atemperature lower than the ignition point. In this case, too, only ashort wait time is required following the ashing process before therestoration process can be executed, since the ignition point of the gasused in the restoration process in the embodiment is 300° C. or higher,which is higher than the ignition points of the gases used in therelated art. As a result, the throughput is not lowered significantly.

In addition, the film quality of the damaged area of the low dielectricconstant insulating film, having become damaged during the etchingprocess or the ashing process, is restored to a desirable condition andthe damaged area can be dehydrated more readily and effectively comparedto the related art.

In the post processing chamber 400 in the embodiment, the cooling block420, which cools the wafer W on the stage 408, is installed and thus,the ashed wafer can be quickly cooled. Specifically, after turning offthe power supply from the heater power source 418 to the heater 416, thecooling block 420 is raised by engaging the elevator device 424 inoperation until the cooling block is placed in close contact with thelower surface of the heater 416 and the wafer W, placed on the uppersurface of the faceplate 412, can thus be cooled quickly. Through thesemeasures, it is ensured that even when the temperature of the waferfollowing the ashing process is higher than the ignition point, thewafer is allowed to quickly cool down to a temperature sufficientlylower than the ignition point. Since the length of wait time to elapsebefore the restoration process is executed is minimized through thetemperature monitoring, better throughput is achieved.

It is to be noted that a further improvement in throughput of therestoration process executed in succession to the ashing process can beachieved by selecting an optimal type of processing gas to be used inthe restoration process in correspondence to the wafer temperatureduring the ashing process. For instance, a gas containing a β-diketonecompound with a higher ignition point may be used when the temperatureof the wafer having undergone the ashing process is higher, so as toensure that the restoration process can be executed with a minimum waittime following the ashing process.

In addition, by adopting the embodiment, which allows both the ashingprocess executed with hydrogen radicals and the restoration process tobe executed in a single post processing chamber 400, the substrateprocessing apparatus 100 equipped with such a post processing chamber400 can be provided as a more compact unit with the available spacetherein utilized more efficiently. Furthermore, the substrate processingapparatus is allowed to include a plurality of post process chambers 400without significantly increasing its installation space. This, in turn,leads to a higher level of reliability of the substrate processingapparatus 100. Namely, in the event of trouble occurring in a given postprocessing chamber 400, the ashing process and the restoration processcan still be executed in another post processing chamber 400. Thus, evenif trouble occurs, the processing on a batch of wafers W can becontinuously executed without having to stop the substrate processingapparatus 100. Consequently, any reduction in the throughput of thesubstrate processing apparatus 100 can be minimized in the event oftrouble. Moreover, since the ashing process and the restoration processcan be executed in succession, concurrently in the plurality of postprocessing chambers 400, a further improvement in the throughput of thesubstrate processing apparatus 100 can be achieved.

(Specific Example of the Film Structure in the Processing Target Wafer)

Next, a specific example of the film structure in the processing targetwafer W to undergo the subsequent of processing (the etching process,the ashing process and the restoration process) at the substrateprocessing apparatus 100 in the embodiment described above is explained.FIG. 4 is a sectional view of a specific example of the film structurein an unprocessed wafer W yet to undergo the processing in the substrateprocessing apparatus 100.

The film structure at the wafer W shown in FIG. 4 includes a pluralityof films formed over a Si substrate (silicon substrate) 510. In morespecific terms, it includes a base insulating film 520 constituted ofSiO₂ or the like, which is formed on top of the Si substrate 510, ametal layer 522 formed by burying, for instance, Cu in the baseinsulating film 520, an etching stopper film 530 constituted of SiC orthe like, which is formed over the base insulating film 520, a low-kfilm 540 formed over the etching stopper film, which is constituted of amaterial containing silicon and has a methyl-group (CH₃ group) skeleton,a capping film 550 formed over the low-k film and constituted of SiO₂ orthe like, an anti-reflection coating (BARC) 560 formed over the cappingfilm and a photoresist film 570 formed over the anti-reflection coating570.

Such a film structure can be achieved at the wafer W by executing filmformation processing and the like in a specific sequence on the Sisubstrate 510 at a substrate processing apparatus (not shown) differentfrom the substrate processing apparatus 100. In addition, after thephotoresist film 570 is formed, the wafer W undergoes a photolithographyprocess and thus, a specific wiring pattern is formed at the photoresistfilm 570.

(Specific Example of Wafer Processing)

Next, in reference to a drawing, the entire sequence of processing thatthe wafer W undergoes at the substrate processing apparatus 100 isdescribed. FIG. 5 presents a flowchart of the processing executed in thesubstrate processing apparatus 100 in the embodiment. The processingsequence is executed on the wafer W at the substrate processingapparatus 100 as the control unit 120 controls the individual unitsbased upon a specific program. The processing sequence to be explainedin reference to the embodiment includes an etching process, an ashingprocess and a restoration process executed in this order on a wafer Wassuming a film structure such as that shown in FIG. 4, which istransferred in a low-pressure environment to the individual processingchambers.

In step S100, the wafer W assuming the film structure shown in FIG. 4having been taken out of a cassette container 102, is transferred to oneof the processing chambers 220A, 220B, 220E and 220F designated asetching process chambers in the substrate processing apparatus 100. Morespecifically, a wafer W in a cassette container 102 is transferred tothe orienter 304 via the transfer unit-side transfer mechanism 320 andthe wafer W is then positioned at the orienter The wafer W having beenpositioned at the orienter 304 is taken back onto the transfer unit-sidetransfer mechanism 320 which then carries it into either the firstloadlock chamber 230M or the second loadlock chamber 230N, e.g., thefirst loadlock chamber 230M. Subsequently, the wafer W in the firstloadlock chamber 230M is carried on the processing unit-side transfermechanism 250 into one of the processing chambers 220A, 220B, 220E and220F designated as the etching process chamber, e.g., the etchingprocess chamber 220A

(Specific Example of the Etching Process)

Next, a specific type of etching process is executed on the wafer W instep S110. The etching process executed in the processing chamber(etching process chamber) 220A is described in specific terms. Aprocessing gas such as CF₄ gas is delivered into the processing chamber220A and high-frequency power is supplied between the electrodesdisposed within the processing chamber 220A so as to generate plasmafrom the processing gas over the wafer. Through this process, theanti-reflection coating 560, the capping film 550, the low-k film 540and the etching stopper film 530 become sequentially and selectivelyetched with the patterned photoresist film 570 used as a mask.

Through the etching process executed as described above, a wiring groove(hereinafter, the term “wiring groove” may also refer to a wiring hole)580 is formed as a recessed portion in the low-k film 540 as shown inFIG. 6. As a result, the surface of the low-k film 540 becomes exposedat the side wall of the wiring groove 580 and the surface of the metallayer 522 becomes exposed at the bottom of the wiring groove 580.

(How the Etching Process may Affect the Low-k Film)

The adverse effects of the etching process that the low-k film may besubjected to are now explained. As the low-k film 540 is etched with theprocess gas such as CF₄ gas, a damaged area is formed near the surfaceof the low-k film 540 exposed at the wiring groove 580 as shown in FIG.6. In the damaged area 542, the CH₃ group decreases through a reactionwith the fluorine contained in the CF₄ gas and the hydroxyl group (OHgroup) increases markedly through a reaction with water, resulting in anincrease in the dielectric constant of the low-k film 540. If such adamaged area 542 is left unrestored, the electrical characteristics ofsemiconductor devices produced as final products from the wafer W may becompromised. It is to be noted that while FIG. 6 schematicallyillustrates the damaged area 542, the boundary of the damaged area 542and an undamaged area is not necessarily as clear as that shown in FIG.6.

In addition, a low-k film is normally constituted of a porous materialhaving a high level of water absorption capacity. Furthermore, low-kfilm 540 will absorb water even more readily over the damaged area 542formed during the etching process, as shown in FIG. 6. This means thatif the wafer W is taken out of the substrate processing apparatus 100immediately after the etching process without first executing therestoration processing to be detailed later, the low-k film 540 in thedamaged state will be exposed at the wiring groove 580. Under suchcircumstances, water in the air will be absorbed readily through thedamaged area 542 into the low-k film 540.

The presence of water 544 in the low-k film 540 degrades the quality ofthe low-k film 540 both with regard to its electrical characteristicsand with regard to its mechanical characteristics. The dielectricconstant of water is higher than that of air and thus, as the quantityof water 544 contained in the low-k film 540 increases, the overalldielectric constant of the low-k film 540 will increase, resulting inpoorer electrical characteristics.

In addition, as the presence of water 544 in the low-k film 540compromises the mechanical strength of the low-k film, the shape of thewiring groove 580 with an extremely small width having been formedthrough etching may lose its intended shape before the wiring metal isembedded therein. Furthermore, various types of films including anotherlow-k film cannot be layered upon the low-k film 540 with loweredmechanical strength in a stable manner. In other words, the low-k film540 may not have the mechanical strength required in a multilayer wiringstructure. Moreover, if the low-k film 540 does not assure a sufficientlevel of strength, the low-k film 540 and the film (e.g., the etchingstopper film 530 or the capping film 550) in contact with the surface ofthe low-k film may become separated from each other.

As semiconductor circuits assume increasingly fine circuit structureswith a greater number of films layered therein, it has become a crucialrequirement in recent years that the low-k film 540 maintain itsmechanical strength as well as its electrical characteristics. For thisreason, it is essential that following the etching process, a process beexecuted so as to ensure that as much water as possible is released fromthe low-k film 540 and that any further absorption of water into thelow-k film 540 is minimized.

Accordingly, a restoration process is executed on the wafer W in theembodiments in order to restore the film quality of the low-k filmdamaged in the etching process to a desirable state before the wafer Wis carried out of the substrate processing apparatus 100 and is exposedto the air.

More specifically, upon completing the etching process (step S110), theetched wafer W is transferred into either the processing chamber 220C or220D, both structured to function as post processing chambers 400, instep S120 in FIG. 5.

(Specific Example of the Ashing Process)

Next, in step S130, a specific ashing process is executed on the wafer Wby using hydrogen radicals. This ashing process is now described inspecific detail in reference to FIG. 3. In preparation for the ashingprocess, to be executed in the processing chamber 220C or 220Dfunctioning as the post processing chamber 400, the gate valve 240 isopened, the wafer W having undergone the etching process, such as thatshown in FIG. 6, is carried into the main processing chamber 402 and thewafer W is placed onto the stage 408. An explanation is given on anexample in which the ashing process is executed in the processingchamber 200C.

Once the wafer W is carried into the processing chamber, the gate valve240 is closed and the main processing chamber 402 and the bell jar 404are evacuated by the exhaust device 436 until the pressure therein islowered to a predetermined level (e.g., 1.5 Torr).

Then, the switching valve 456 is opened and a specific ashing processinggas, e.g., a mixed gas containing hydrogen gas and helium gas (with thehydrogen gas mixed at a ratio of, for instance, 4%) is delivered fromthe ashing processing gas supply source 450 via the ashing processinggas supply piping 452 and the processing gas supply piping 444 into thebell jar 404. The flow rate of the ashing processing gas is adjusted viathe mass flow controller 454.

In addition, high-frequency power (e.g., 4000 W) is supplied from thehigh-frequency power source 442 to the coil 440. As a result, plasma isformed inside the bell jar 404 under stable conditions and hydrogenradicals H* are generated. The hydrogen radicals H* are then supplieddownward toward the wafer W placed on the stage 408 within the mainprocessing chamber 402 located below.

With the heater 416 pre-heated by controlling the heater power source418, the wafer W is heated to a predetermined temperature (e.g., aprocessing temperature of 250° C.) optimal for the ashing process andthe heated wafer sustains the specific temperature.

As the hydrogen radicals are delivered toward the wafer W sustaining thepredetermined temperature (e.g., 250° C.) in the post processing chamber400, the wafer W undergoes the ashing process. FIG. 7 shows the filmstructure of the wafer W having undergone the ashing process. As shownin FIG. 7, the photoresist film 570 and the anti-reflection coating 560are removed from the wafer W through the ashing process.

Once the photoresist film 570 and the anti-reflection coating 560 areremoved, the switching valve 456 is closed to stop the delivery of theashing processing gas from the ashing processing gas supply source 450into the bell jar 404 and also the output of the high-frequency powerfrom the high-frequency power source 442 to the coil 440 is turned off.In addition, the output of the power from the heater power source 418 tothe heater 416 is lowered or stopped. The ashing process is thuscompleted.

In addition, since the wafer W is heated to a relatively hightemperature of, for instance, 300° C. during the ashing process, water544 present in the low-k film can be released as well as water presentat the surface of the low-k film 540, in addition to removing thephotoresist film 570 and the anti-reflection coating 560 as describedabove. However, if the temperature of the wafer W becomes excessivelyhigh, the low-k film 540 will be thermally degraded. Accordingly, it isdesirable to set the predetermined temperature to be achieved at thewafer W during the ashing process within a range of 250° C.˜400° C.,over which water 544 can be efficiently released from the low-k film 540without degrading the low-k film 540.

If a fluorine-containing gas such as CF₄ gas is used as the processinggas for the etching process executed prior to the ashing process, themetal (e.g. copper) constituting the metal layer 522 exposed at thebottom of the wiring groove 580 will react with the fluorine containedin the processing gas, resulting in the formation of an undesirablemetal compound film (e.g., a CuF film) at the exposed surface. If such ametal compound film is present over the area where the wiring metal,such as copper, to be embedded at the wiring groove 580 in a subsequentstep, is to connect with the metal layer 522, the electrical resistanceover the connecting area will increase and, as a result, desirableelectrical characteristics cannot be assured in the multilayer wiringstructure.

The embodiment addresses this issue by executing a specific type ofashing process through which any metal compound film (e.g., a CuF film)present over the exposed surface of the metal layer 522 is reduced andremoved with the hydrogen radicals. Since the exposed surface of themetal layer 522 is thus cleaned and is restored as a pure metal surface,the surface resistance is greatly lowered.

In the ashing process in the related art, plasma raised from anoxygen-containing gas (hereinafter may also be referred to as“oxygen-containing plasma”) is often used. However, during the ashingprocess executed by using such oxygen plasma, the low-k film 540 tendsto be damaged by oxygen radicals. Namely, the oxygen radicals, which arehighly reactive, react with the CH₃ group in the low-k film 540 andthrough this reaction, an OH group is formed. Such damage is extremelydifficult to repair. More specifically, a chemical reaction involvingoxygen radicals occurs around the damaged area 542 of the low-k film 540having become damaged during the etching process. The oxygen radicalspenetrate the low-k film 540 through the exposed surface to form an areadensely packed with Si—O (to be referred to as a “shrink layer” in thedescription). The shrink layer formed over the damaged area 542 makes itdifficult to fully recover from the damage in the damaged area 542,since the shrink layer hinders full penetration of the processing gasduring the subsequent restoration process.

In contrast, the hydrogen-containing gas with no oxygen atom content isutilized in the ashing process in the embodiment. This means that sinceno oxygen radicals are generated, a shrink layer is not formed over thedamaged area 542 in the low-k film 540 and instead, Si—H bonds arepresumably formed in the damaged area 542. The Si—H bond can be easilyreverted to the initial Si—CH₃ state through the use of DPM gas oracetylacetone gas. Accordingly, by using DPM gas or acetylacetone gas asthe processing gas in the restoration process executed after the ashingprocess, the film quality in the damaged area 542 of the low-k film 540can be restored to a good condition.

Through the ashing process executed in the embodiment as describedabove, the water 544 present in the low-k film 540 can be removed andthe exposed surface of the metal layer 522 can be cleaned, as well asremoving the photoresist film 570 and the anti-reflection coating 560from the wafer W, which is the main purpose of the process. In addition,the composition of the low-k film 540 over the damaged area 542 can bealtered so that the damaged area 542 is more effectively restoredthrough the restoration process.

As shown in FIG. 5, following the ashing process (step S130) executed onthe wafer W in the processing chamber 220C functioning as the postprocessing chamber 400, a decision is made in step S140 as to whether ornot the temperature of the wafer W is equal to or higher than apredetermined level. In the embodiment, the temperature of the wafer Wis detected before delivering the restoration gas into the processingchamber 220C, so as to ensure that no ignition of the restoration gasdelivered into the processing chamber 220C for the subsequentrestoration process, does not occur. Accordingly, it is desirable topreselect a temperature setting within a range lower than the ignitionpoint of the restoration processing gas, as the predeterminedtemperature.

The predetermined temperature should be set by allowing a considerablemargin in correspondence to the ignition point of the restorationprocessing gas. For instance, the predetermined temperature may be setto 250° C. in conjunction with the DPM gas with an ignition point ofapproximately 300° C. used as the restoration processing gas, therebyallowing a margin of 50° C. under the 300° C. ignition point.Alternatively, the predetermined temperature may be set to 260° C.,thereby allowing a margin of 40° C. In addition, the predeterminedtemperature may be set to 300° C. in conjunction with the acetylacetonegas with an ignition point of approximately 350° C. used as therestoration processing gas, thereby allowing a margin of 50° C. underthe 350° C. ignition point, or the predetermined temperature may be setto 3 10° C., thereby allowing a margin of 40° C. By selecting thepredetermined temperature in reference to which a decision as to whetheror not to further cool the wafer W is made, in correspondence to theignition point of the specific restoration processing gas, as describedabove, it is ensured that the wafer W is not cooled to an unnecessarilylow temperature prior to the restoration process.

If it is decided in step S140 that the temperature of the wafer W islower than the predetermined level, the temperature of the wafer isjudged to be at a level at which the restoration processing gasdelivered into the processing chamber will not ignite and accordingly,the restoration process is immediately started in step S160. If, on theother hand, it is decided in step S140 that the temperature of the waferW is equal to or higher than the predetermined level, the wafer W iscooled in step S150 until its temperature becomes lower than thepredetermined level prior to the restoration process.

As described above, if the temperature of the wafer W having undergonethe ashing process is already considerably lower than the ignition pointof the restoration processing gas, the restoration process is startedimmediately without cooling the wafer following the ashing process. Inaddition, it is ensured that even when the temperature of the wafer Wfollowing the ashing process is higher than the ignition point, thewafer W is allowed to cool down to a temperature sufficiently lower thanthe ignition point. Since the length of wait time to elapse before therestoration process is executed is minimized through the temperaturemonitoring, a significant improvement in throughput is achieved over therelated art in which the ashing process and the restoration process areexecuted in separate processing chambers.

While control unit 120 in the embodiment indirectly measures thetemperature of the wafer W via a temperature sensor head such as thethermocouple 432 installed at the faceplate 412, the present inventionis not limited to this example. For instance, another temperature sensorhead may be installed at an area inside the processing chamber 220Cwhere the temperature rises to a level higher than the temperature ofthe wafer W and, in conjunction with the additional temperature sensorhead, the control unit may determine the optimal timing with which therestoration processing gas should be delivered by taking intoconsideration the measurement results provided by the additionaltemperature sensor head as well.

(Specific Example of Wafer Cooling)

A specific example of the processing executed to cool the wafer W (stepS150) is now described. When cooling the wafer W, the output of thepower from the heater power source 418 to the heater 416 is firstlowered or stopped and the cooling block 420 is raised by engaging theelevator device 424 in operation until the cooling block comes intoclose contact with the lower surface of the heater 416. The coolantsupplied from the outside, the temperature of which is pre-adjusted to,for instance, 25° C., circulates through the cooling block 420. Thus,the wafer W can be cooled with the cooling block 420 via the faceplate412 and the heater 416 simply by placing the cooling block 420 in closecontact with the lower surface of the heater 416. As a result, even whenthe temperature of the wafer W is equal to or higher than thepredetermined temperature mentioned earlier, the overall wafer W can beeasily and rapidly cooled to a temperature lower than the predeterminedlevel (e.g., 260° C.). This means that the length of wait time to elapsebefore the start of the restoration process following the ashing processcan be reduced. For instance, a hydrogen radical processing such as theashing process described above is executed by raising the temperature ofthe wafer to a high level (e.g., 250° C.˜400° C.). Depending upon theprocessing conditions selected for the hydrogen radical processing, thewafer temperature may be raised even higher, to 400° C.˜600° C. Evenunder such circumstances, the temperature of the wafer cooled with thecooling block 420 can be rapidly lowered to a level considerably lowerthan the ignition point of the restoration gas.

Once the temperature of the wafer W is lowered to the predeterminedtemperature level, the elevator device 424 is driven to move the coolingblock 420 downward away from the lower surface of the heater 416. Thelevel of the power supplied from the heater power source 418 to theheater 416 is controlled so as to sustain the temperature of the wafer Wat a predetermined level (e.g., a processing temperature of 250° C.),optimal for the subsequent restoration process.

Through the cooling process described above, the ashed wafer W, thetemperature of which may still be fairly high, can be rapidly cooled,allowing the restoration process to start as soon as possible. Inaddition, as long as the temperature of the wafer W is already lowerthan the predetermined temperature at the end of the ashing process, therestoration process can be started immediately without cooling the waferW. For instance, provided that the predetermined temperature is set at260° C., as described earlier, the restoration process can be startedwithout having to cool the wafer W if the temperature of the ashed waferW is 250° C. Since the elevator device 424 does not have to be driven toraise the cooling block 420, the length of wait time to elapse beforethe restoration process start can be further reduced in this situation.

(Specific Example of the Restoration Process)

Next, a specific example of the restoration process (step S160) isdescribed in reference to drawings. As explained earlier, therestoration process is executed in the same processing chamber 220Cfunctioning as the post processing chamber 400 where the wafer W hasalready undergone the ashing process, without transferring the wafer Wto another processing chamber.

When executing the restoration process in the processing chamber 220C(post processing chamber 400), the processing chamber 220C is evacuatedby the exhaust device and the pressure therein is lowered to apredetermined level (e.g., 50 Torr). Then, the switching valve 466 isopened and a specific restoration processing gas, e.g., DPM gas oracetylacetone gas is delivered from the restoration processing gassupply source 460 via the restoration processing gas supply piping 462and the processing gas supply piping 444 into the bell jar 404. The flowrate of the restoration processing gas, is adjusted via the mass flowcontroller 464.

In addition, the temperature of the wafer W is sustained via the heater416 at the optimal level (e.g., a processing temperature of 250° C.) forthe restoration process. As a β-diketone compound-containing gasconstituting the restoration processing gas, such as acetylacetone gas,is delivered into the processing chamber 220C in this state, the wafer Wundergoes the restoration process. FIG. 8 shows the film structure ofthe wafer W having undergone the restoration process.

As the restoration process is executed by using the restorationprocessing gas as described above, a chemical reaction occurs over thedamaged area 542 of the low-k film 540 and through the chemicalreaction, the film quality of the damaged area 542 is restored to adesirable condition, as shown in FIG. 8. Furthermore, through the ashingprocess executed as described above by using hydrogen radicalsimmediately before the restoration process in the embodiment, thedamaged area 542 of the low-k film 540 has been rendered into a state inwhich the damaged area readily assumes a CH₃ group composition, allowingthe damaged area 542 to become fully repaired.

The film quality in the damaged area 542 is restored to the initialdesirable condition and, as a result, the damaged area 542 disappears.In addition, the terminal at the surface of the low-k film 540 exposedat the wiring groove 580 takes on a CH₃ group composition and, as aresult, a water repellent layer 546 is formed. This water repellentlayer 546 prevents absorption of any additional water into the exposedsurface of the low-k film 540 and prevents the low-k film 540 from beingpenetrated by water.

Now, the mechanism of the reaction occurring as the film quality in thedamaged area 542 of the low-k film 540 is restored by usingacetylacetone gas as the restoration processing gas is described inreference to relevant chemical reaction formulae.

The acetylacetone contained in the acetylacetone gas delivered into theprocessing chamber 220C releases protons through the keto-enolequilibrium, as expressed in chemical formula (1) below.

It is assumed that the damaged area 542 of the low-k film 540, where arelatively large quantity of water is present, has an excessivelydominant presence of silanol radicals (SiOH group). As indicated inchemical formula (2) below, a dehydration reaction is induced in thedamaged area 542 by the protons released from the acetylacetone andacting on the SiOH group.

The acetylacetonate formed as the protons are released from theacetylacetone configures a protective group for the dangling bond ofsilicone formed as water (H₂O) departs the damaged area 542, asindicated in chemical formula (3) below.

The α hydrogen in the CH₃ group cannot be dissociated readily undernormal circumstances. However, in the damaged area 542 where the SiOHgroup is assumed to be present in large quantity near the CH₃ group, thea hydrogen reacts with the OH group contained in the silanol group andthus moves out of the CH₃ group as indicated in chemical formula (4).

The CH₃ group from which the a hydrogen has been dissociated asdescribed above becomes bonded with the silicone having the danglingbond formed over the damaged area 542 through the chemical reactionexpressed in chemical formula (2). As a result, a bridge structure isformed and the film quality of the damaged area 542 is restored to goodcondition, as indicated in chemical formula (5) below.

As described above, by using acetylacetone gas as the restorationprocessing gas, water present in the damaged area 542 of the low-k film540 can be effectively removed and the film quality can be restored togood condition. In addition, since five atoms of carbon (C) areaccommodated at each bridge, better hydrophobicity compared to therelated art is achieved. A dehydration effect and a hydrophobicityeffect similar to those described above can also be realized by usinganother β-diketone compound-containing gas such as DPM gas as therestoration processing gas.

In the embodiment described above, a hydrogen-containing gas is used asthe ashing processing gas during the ashing process so as to ensure thatno shrink layer is formed over the damaged area 542. In addition, sincea β-diketone compound-containing gas such as DPM gas or acetylacetonegas is used as the restoration processing gas during the restorationprocess, any shrunken structure attributable to a shrink layer that mayhave been formed over the damaged area 542 can be expanded. As a result,the restoration processing gas can be delivered to penetrate the damagedarea 542 over a wide range, so as to restore the film quality of thedamaged area 542 even more reliably.

The use of a β-diketone compound-containing gas as the restorationprocessing gas has the following advantages over the related art, inwhich a silylating gas is used. First, a silylating gas often containsammonia radicals (NH₃ group), giving rise to a concern that ammoniasalt, which can settle as particles on the wafer, may be formed. Incontrast, the β-diketone compound-containing gas does not contain anyammonia group and is thus more desirable than a silylating gas, sincethere will be no formation of ammonia salt.

The process through which the use of a silylating gas results in theformation of ammonia salt and ultimately particles settled onto thewafer W, is now described. FIGS. 9A˜9D illustrate the process throughwhich particles settle on the wafer W having undergone the etchingprocess.

A gas constituent (e.g., a halogen gas constituent containing, forinstance, F, Br or Cl) in the etching processing gas may become bondedat the surface of the etched wafer W and thus form a compound. Thepresence of such a compound on the wafer W may result in the formationof particles (reaction products) on the wafer W, particularly if theatmosphere surrounding the etched wafer W contains ammonia.

First, as a constituent of the etching processing gas becomes adheredonto the surface of the wafer W having undergone the etching process,the gas constituent of the etching processing gas and the substanceconstituting the surface of the wafer W bond with each other, therebyforming a compound A, as shown in FIG. 9A. For instance, if the etchingprocessing gas contains a halogen gas constituent (e.g., F, Br or Cl),the halogen gas constituent may bond with, for instance, SiO₂ on theprocessed wafer W, thereby forming a compound A on the wafer W.

If the restoration processing gas delivered toward the wafer Wsubsequently undergoing the restoration process has, for instance, anamine content, the halogen compound in the compound A at the wafer Wreacts with the amine content in the restoration processing gas and, asa result, salt B is formed on the surface of the wafer W, as shown inFIG. 9B. The amine content includes, for instance, ammonia, amine andthe like. The amine may be, for instance, trimethyl amine, triethylamine or an organic basic amine.

The sequence of the process through which the salt B is formed at thesurface of the wafer W is expressed in chemical formulae (6)˜(8) below.The chemical formulae below represent a process through which thesubstance (SiO₂) present at the surface of the wafer W bonds with a gasconstituent (HF) of the etching processing gas, thereby forming acompound (SiF₄), the compound (SiF₄) reacts with ammonia (NH₃) in therestoration processing gas and halogen ammonia salt (e.g., (NH₄)₂SiF₆)is formed.SiO₂+4HF→SiF₄+2H₂O   (6)SiO₂+4HF+4NH₃→SiF₄+2H₂O+4NH₃   (7)SiF₄+2HF+2NH₃→(NH₄)₂ SiF₆   (8)

It is generally assumed that when the substance (SiO₂) present at thesurface of the wafer W bonds with a gas constituent (HF) in the etchingprocessing gas and a compound (SiF₄) is formed, the reaction expressedin chemical formula (6) occurs.

However, if ammonia (HF3) is present in the restoration processing gas,the reaction expressed in chemical formula (7) may also occur. While thelevel of the reaction energy required to shift from the state on theleft side to the state on the right side in chemical formula (6) is 1.0eV, the level of reaction energy required to shift from the state on theleft side to the state on the right side in chemical formula (7) is only0.4 eV, far lower than that required in the reaction expressed inchemical formula (6).

Thus, if there is ammonia (NH₃) present in the restoration processinggas, the reaction expressed in chemical formula (7) becomes moredominant, and, as a result, the compound (SiF₄) will be formed morereadily on the surface of the wafer W. This, in turn, prompts thereaction expressed in chemical formula (8), inducing ready formation ofhalogen ammonia salt ((NH₄)₂SiF₆).

As described above, if the wafer W, with a halogen gas constituentadhering thereto is exposed to a restoration processing gas containingammonia (NH₃), halogen ammonia salt (e.g., (NH₄)₂SiF₆) will be formed onthe surface of the wafer W.

The salt B such as halogen ammonia salt formed on the surface of thewafer W as described above gradually absorbs water (H₂O) in theatmosphere surrounding the wafer W. As time elapses, particles C areformed as shown in FIG. 9C. Namely, very small particles C,approximately 0.001 μm in diameter, too small to be detected eventhrough an electron microscope, are initially formed and their quantitygradually increases while their size also gradually increases. Afterapproximately one hour, for instance, they will have grown in size toapproximately 0.1 μm. In 24 hours, some particles C may have grown to aslarge as 0.5˜0.7 μm.

A few days later, the salt B will have become deliquesced in the water(H₂O) in the atmosphere and thus will have coagulated. If particles Ccontain, for instance, SiO₂, a residue D of SiO₂ will remain on thewafer W after the particles C evaporate as shown in FIG. 9D. It is to benoted that the particles C with no SiO₂ content will evaporate anddisappear without leaving any residue.

In addition to the issue discussed above, there is a concern arisingwhen a silylating gas containing ammonia is used as the restorationprocessing gas. Namely, as the wafer W is etched with CF₄ gas, thewiring groove 580 is formed as a recessed area in the low-k film 540, asshown in FIG. 6. Through the etching process, the surface of the metallayer 522 becomes exposed at the bottom of the wiring groove 580. A verysmall amount of fluorine (CF) in the CF₄ gas may remain at the exposedsurface of the metal layer 522. As the restoration process issubsequently executed on the wafer W with a restoration processing gascontaining ammonia, the fluorine and the ammonia may react with eachother, resulting in the formation of NH₄F (solid substance) at theexposed surface of the metal layer 522. If a wiring metal such as copperis embedded in the wiring groove 580 in this state, the presence of NH₄Fat the connecting area where the wiring metal and the metal layer 520connect with each other will increase the electrical resistance over theconnecting area.

The β-diketone compound-containing gas, such as DPM gas or acetylacetonegas, used in the restoration process in the embodiment does not containany ammonia, and thus, even if a very small amount of fluorine ispresent at the exposed surface of the wafer W, NH₄F, (NH₂)₄SiF₆ or thelike is not formed. Consequently, the formation of particles isprevented and the electrical resistance over the area where the wiringmetal and the metal layer 522 connect with each other is kept at a lowlevel, thereby assuring desirable electrical characteristics in themultilayer wiring structure.

It is to be noted that since the wafer W is allowed to sustainrelatively high temperature (e.g., 250° C.) during the restorationprocess in the embodiment, any residual water 544 in the low-k film 540can be removed during the restoration process.

Once the restoration process executed in step S160 ends, the wafer W iscarried out of the processing chamber 220C via the processing unit-sidetransfer mechanism 250 installed in the common transfer chamber 210 andis carried into either the first loadlock chamber 230M or the secondloadlock chamber 230N, e.g., the second loadlock chamber 230N. The waferW carried into the second loadlock chamber 230N is then taken back intothe initial cassette container 102 via the transfer unit-side transfermechanism 320. The sequence of wafer processing in the embodiment thusends. The wafer W taken back into the cassette container 102 issubsequently transferred to another substrate processing apparatus (notshown) to undergo a specific process, e.g., a copper embedding processthrough which a wiring metal such as copper is embedded into the wiringgroove 580 formed in the low-k film 540.

As described above, the wafer processing in the embodiment is executedby using, as a restoration processing gas, a β-diketonecompound-containing gas (e.g., DPM gas or acetylacetone gas) containinga β-diketone compound with an ignition point higher than those ofsilylating gases used in the related art. Thus, both the ashing processand the restoration process can be executed in succession on the wafer Win the processing chamber 220C structured to function as the postprocessing chamber 400. As a result, the throughput of the substrateprocessing apparatus 100 is improved.

In addition, by adopting the embodiment, the film quality of the low-kfilm 540 having been damaged during the etching process or the ashingprocess can be restored to a desirable condition and the damaged areacan be rendered into a sufficiently hydrophobic state.

The results of tests conducted to verify the advantages achieved byexecuting the restoration process in the embodiment are now described.In the tests, test wafers were each carried into an etching processchamber and the low-k film on the wafer was etched in a specificpattern. The test wafer was then transferred from the etching processchamber to the post processing chamber 400 where it underwent an ashingprocess to remove the etching mask. The restoration process and theashing process were executed in succession in the same post processingchamber 400 by using a DPM gas as the restoration processing gas. Inaddition, in order to verify the relationship between the temperature ofthe test wafer undergoing the restoration process and the extent ofrestoration of the low-k film, the restoration process was executed byadjusting the test wafer temperature to 150° C., 200° C. and 250° C.

The results of the tests conducted to verify that the film quality ofthe low-k film 540 is restored through the restoration process in theembodiment, i.e., that the dielectric constant is recovered to adesirable level, are first described. The decision as to whether or notthe film quality of the low-k film 540 has been restored may be made by,for instance, measuring the dielectric constant of the low-k film 540both before and after the restoration process. FIG. 10 presents theresults obtained by measuring the dielectric constant (k value) of thelow-k film. It is to be noted that the dielectric constant of the low-kfilm used in the tests was 2.38 prior to the etching process.

As FIG. 10 indicates, the dielectric constant of the low-k film on thetest wafer W having undergone the etching process and the ashing processbut not yet the restoration process increased to a level exceeding 3.0from the pre-etching process value of 2.38, indicating that the filmquality had degraded significantly. With the DPM gas supplied as therestoration processing gas to the low-k film with the undesirably highdielectric constant, the film quality was restored with the dielectricconstant lowered to a level below 2.8, regardless of the temperature ofthe wafer W undergoing the restoration process, 150° C., 200° C. or 250°C. In particular, the film quality was restored to a more significantextent through the restoration process with the dielectric constantlowered to 2.6, when the temperature of the wafer W was set at 250° C.

Next, the results of tests conducted to verify that the damaged area ofthe low-k film 540 is rendered into a sufficiently hydrophobic statethrough the restoration process in the embodiment are described. Thisverification may be executed by measuring the contact angle of the low-kfilm both before and after the restoration process. FIG. 11 presents agraph indicating such measurement results. In the test, a liquid such aswater was dropped onto the surface of the low-k film and the angle(contact angle) formed by the tangential line of the liquid droplet andthe surface of the low-k film was measured. If the low-k film had ahigher level of hydrophobicity, the droplet on the film would assume amore spherical shape due to its own surface tension and thus the contactangle would be larger. More specifically, the level of hydrophobicity ofthe low-k film would be judged to be higher when the contact angle wascloser to 90°, whereas the level of hydrophilicity of the low-k filmwould be judged to be higher (the level of its hydrophobicity judged tobe lower) when the contact angle was closer to 0°.

As shown in FIG. 11, the contact angle of the low-k film on the testwafer W having undergone the etching process and the ashing process butnot yet the restoration process was less than 10°. The hydrophobicity ofthe low-k film in this state would be very low and water would bereadily absorbed into the low-k film. With the DPM gas supplied as therestoration processing gas to the low-k film with the loweredhydrophobicity, the contact angle was increased significantly to valuesabove 60°, indicating an improvement in the hydrophobicity of the low-kfilm, regardless of the temperature of the wafer W undergoing therestoration process, 150° C., 200° C. or 250° C.

As the test results described above illustrate, the film quality of thelow-k film having been damaged during the etching process can berestored to good condition through a restoration process executed byusing a β-diketone compound-containing gas such as DPM gas oracetylacetone gas, so as to assure better electrical characteristics andmechanical characteristics over the related art. This, in turn, makes itpossible to form semiconductor devices with desirable characteristics onwafers.

It is to be noted that while an explanation is given above in referenceto the embodiment on an example in which the substrate processingapparatus 100 includes four etching process chambers and two postprocessing chambers 400, the present invention is not limited to thisexample and the numbers of the two types of processing chambers areadjustable. In addition, it is not essential that the substrateprocessing apparatus 100 include etching process chambers, and instead,the substrate processing apparatus 100 may include a post processingchamber 400 alone. In such a case, the etching process may be executedin a separate substrate processing apparatus.

Furthermore, while the wafer W undergoing the processing in theembodiment includes the anti-reflection coating 560 formed thereupon,such an anti-reflection coating 560 is not an essential requirement ofthe present invention. In addition, while the embodiment of the presentinvention has been explained in reference to an example in which theprocessing target substrate is a semiconductor wafer, the presentinvention is not limited to this example and it may be adopted inconjunction with another type of substrate.

It is obvious that the present invention may be achieved by providing asystem or an apparatus with a medium such as a storage medium havingstored therein a software program for realizing the functions of theembodiment described above and enabling a computer (a CPU or an MPU) inthe system or the apparatus to read out and execute the program storedin the medium such as a storage medium.

The functions of the embodiment described above are achieved in theprogram itself, read out from the medium such as a storage medium,whereas the present invention is embodied in the medium such as astorage medium having the program stored therein. The medium such as astorage medium in which the program is provided may be, for instance, aflexible disk, a hard disk, an optical disk, a magneto-optical disk, aCD-ROM, a CD-R, a CD-RW, a DVD-ROM, a DVD-RAM, a DVD-RW, a DVD+RW,magnetic tape, a nonvolatile memory card or a ROM, or the program may bedownload to a storage medium via a network.

It is to be noted that the scope of the present invention includes anapplication in which an OS or the like operating on a computer executesthe actual processing in part or in whole in response to theinstructions in the program read out by the computer and the functionsof the embodiment are achieved through the processing thus executed, aswell as an application in which the functions of the embodiments areachieved as the computer executes the program it has read out.

The scope of the present invention further includes an application inwhich the program read out from the medium such as a storage medium isfirst written into a memory in a function expansion board loaded in acomputer or a function expansion unit connected to the computer, a CPUor the like in the function expansion board or the function expansionunit executes the actual processing in part or in whole in response tothe instructions in the program and the functions of the embodimentdescribed above are achieved through the processing.

While the invention has been particularly shown and described withrespect to a preferred embodiment thereof by referring to the attacheddrawings, the present invention is not limited to this example and itwill be understood by those skilled in the art that various changes inform and detail may be made therein without departing from the spirit,scope and teaching of the invention.

1. A substrate processing method adopted when executing processing on aprocessing target substrate that includes a low dielectric constantinsulating film, an etching mask formed on said low dielectric constantinsulating film and a recessed portion formed by etching with saidetching mask, the recessed portion having a dielectric constant which isincreased from an initial value of said low dielectric constantinsulating film before said etching, the method comprising: an ashingprocess step in which the processing target substrate is heated tosustain a predetermined temperature, and said etching mask is removedthrough ashing with hydrogen radicals delivered to said processingtarget substrate; and a restoration process step in which an area ofsaid low dielectric constant insulating film exposed at said recessedportion, having been rendered hydrophobic and having an increaseddielectric constant value induced by said etching, is restored such thatthe dielectric constant of the area is decreased toward said initialvalue with a β-diketone compound-containing gas that contains aβ-diketone compound with an ignition point equal to or higher than 300°C. that is delivered to said processing target substrate havingundergone said ashing process, wherein said ashing process and saidrestoration process are executed within a single processing chamber. 2.A substrate processing method according to claim 1, further comprisingmeasuring the temperature of said processing target substrate followingsaid ashing process step, wherein: said restoration process is executedimmediately, if the measured temperature of said processing targetsubstrate is lower than a predetermined temperature set within a rangelower than the ignition point of the gas used in said restorationprocess; and said restoration process is executed only after saidprocessing target substrate is cooled to a temperature lower than saidpredetermined temperature, if the temperature of said processing targetsubstrate is equal to or higher than said predetermined temperature. 3.A substrate processing method according to claim 1, wherein saidβ-diketone compound is dipivaloylmethane (DPM) or acetylacetone.